Energy, Exergy, and Economic (3E) Analysis of SOFC-GT-ORC Hybrid Systems for Ammonia-Fueled Ships

A feasible solid oxide fuel cell–gas turbine–organic Rankine cycle (SOFC-GT-ORC) hybrid system for ammonia-fueled ships is presented in this study. To confirm the quantitative changes in thermodynamic performance and economics according to the system configuration, the system using ammonia fuel was simulated, and energy, exergy, and economic (3E) analyses were performed. As a result, the system economics generally had an inversely proportional relationship with the thermodynamic performance. System optimization was performed using a multi-objective genetic algorithm, setting the conflicting thermodynamic performance and economics as objective functions. The key results of this study obtained through optimization are as follows. With the introduction of the ORC, the SOFC-GT hybrid system thermal efficiency was increased by 2–6%, but the cost increased by 14–24%. In the SOFC-GT-ORC hybrid system, preferentially reducing the irreversibility of the SOFC, combustor, and ORC evaporator is advantageous in terms of performance. It is economical to use a moderate amount of SOFC fuel to achieve the target output; the cost of the ORC in the SOFC-GT-ORC hybrid system was approximately $23/h. This study is unique in that it systematically conducted a 3E analysis, which had not been previously well-performed for SOFC hybrid systems for ammonia-fueled ships.